s-Triazine (1,3,5-triazine) and pyrimidine derivatives have been researched in the fields of synthetic resins, synthetic fibers, dyes and agricultural chemicals and a number of such compounds have been synthesized. In the field of pharmaceuticals, researches have been made with respect to antitumor, anti-inflammatory, analgesic and antispasmodic activities. Especially, hexamethylmelamine (HMM) is well-known which has been developed as analogue of antitumor agent triethylenemelamine (TEM) [B. L. Johnson et al. Cancer, 42: 2157-2161 (1978)].
TEM is known as alkylating agent and is an s-triazine derivative having cytotoxic antitumor activity. HMM has been marketed in Europe under the indications for the treatment of ovarian and small cell lung cancers, and its action on solid cancers have attractive.
Among the s-triazine derivatives, imidazolyl-s-triazine derivatives which exhibit cytotoxic and selective aromatase inhibitory activities have been proposed as medicine for estrogen-dependent diseases such as endometriosis, multicystic ovarium, mastosis, endometrium carcinoma and breast cancer (PCT international publication WO93/17009).
However, there is still room for improvement on HMM with respect to its antitumor spectrum and intensity of antitumor activities against solid cancers. As to imidazolyl-s-triazine derivatives, they are limitative in application since they exhibit considerably higher aromatase inhibitory activities than their cytotoxic activities and application of them to cancerous patients other than those who suffer from estrogen-dependent diseases may lead to development of secondary effects such as menstrual disorders due to lack of estrogen. There are still, therefore, strong demands on medicines with no aromatase inhibitory activities and effective for solid cancers.